1. Field of the Invention
The present invention relates to a method of manufacturing a liquid ejection head and a liquid ejection head and more particularly to a method of manufacturing an ink jet print head and an ink jet print head.
2. Description of the Related Art
A liquid ejection head, for example, an ink jet print head used in an ink jet printing apparatus, is known to form ink droplets and eject them by a variety of methods.
As one example use of the ink jet print head (also referred to simply as a print head), Japanese Patent Laid-Open No. 54-051837 (1979) discloses an ink jet printing method that applies thermal energy to the liquid to produce a force for liquid ejection. This printing method heats the liquid by the thermal energy to produce a bubble which in turn forces an ink droplet out of an orifice at the front end of the print head, sending the droplet flying onto a print medium to form an image. This type of print head can relatively easily increase the density of multiple nozzles, allowing for improved resolution, higher print quality and faster printing.
The print head generally has ejection openings from which to eject a liquid, liquid paths leading to the ejection openings, and heating portions arranged one in each of the liquid paths. The heating portion is a means to generate thermal energy when it is energized. The heating portion is formed of a heating resistor layer and protected from ink by an upper protective layer disposed over the heating portion. The heating portion also has a lower layer to accumulate the heat the heating portion has generated for ink ejection.
Generally, the heating portion is made by forming a heat accumulation layer over a silicon substrate, forming a heating resistor layer and an electrode layer over the heat accumulation layer, patterning these layers using photolithography, and then forming an upper protective layer over these layers.
In the heating portion, the electrode layer is formed over the heating resistor layer and is partly removed so that the remaining part of the electrode layer carries an electric current. These layers of the heating portion are protected by the upper protective layer. However, if differences in height formed as a result of partly removing the electrode layer are badly covered with the protective layer, ink may enter from these badly covered stepped portions, leading to a corrosion of electrodes and, in extreme cases, resulting in the electrodes being broken.
Further, as disclosed in Japanese Patent Laid-Open No. 10-338798 (1998), the ink jet print head is made by bonding, with adhesives, a plate (nozzle forming member) having a wall portion in which to form nozzles to the substrate (heater substrate) in which heating resistors are formed. Further, as disclosed in Japanese Patent Laid-Open No. 5-330066 (1993), the ink jet print head can also be made by forming a nozzle forming member of an organic material on the heater substrate.
The print heads described above, however, have a drawback that head constituting members may peel off. In the constructions described in the above Japanese Patent Laid-Open Nos. 10-338798 (1998) and 5-330066 (1993), the nozzle forming member and the heater substrate are made of different materials, so a long period of ink's corrosive attack results in an ingress of ink between the two materials. More specifically, the heater substrate is generally formed of an inorganic material while the nozzle forming member is generally formed of an organic material and a low bonding force between the different materials is considered a major culprit.